Fluid operated electric switch



Oct. 3, 1967 I R. F. SCHABER I 3,345,479

FLUiD OPERATED ELECTRIC SWITCH Filed Oct. 20, 1965 INVENTOR.

P4222? F SCZQZM BY United States Patent OfiFice 3,345,479 FLUID OPERATED ELECTRIC SWITCH Ralph F. Schaber, Warren, Mich, assignor to Chrysler Corporation, Highland Park, Mich, a corporation of Delaware Filed Oct. 20, 1965, Ser. No. 498,733 3 Claims. (Cl. 20083) This invention relates generally to a fluid operated electric switch and more particularly to a fluid operated switch adapted for use in combination with, for example, automobile engine lubrication systems for indicating, as by the making and breaking of an associated electrical system, the non-attainment and attainment of a predetermined minimum lubricant pressure.

Fluid operated switches usually employ a flexible diaphragm which reacts, because of fluid pressure thereagainst, to move an electrical contact in order to make or break an electrical circuit. In order to reduce hysteresis, such flexible diaphragms have been steadily reduced in thickness.

Diaphragm type of pressure responsive switches are often employed in automobiles in connection with vehicle engine lubricating systems in order that the switch may indicate to the vehicle operator conditions of insuflicient or suflicient oil pressure as by the energization and deenergization of a dash panel mounted light bulb. In such arrangements, the pressure responsive flexible diaphragm member of the switch assembly is exposed to cyclic operation during normal vehicle operation and further exposed to hydraulic pulsations often arising out of the tuning characteristics of the engine lubricating system. This means, of course, that during cyclic operation the diaphragm member is first exposed to substantially no or extremely low pressure while at other times being exposed to relatively high pressure as when sufficient lubricating pressure is obtained. The pulsations which the diaphragm experiences are often in addition to the forces developed against the diaphragm during periods when said relatively high pressure is directed thereagainst.

Investigation has shown that extremely small but discernible cracks have been found in the pressure responsive diaphragm and that such cracks permit leakage of hydraulic fluid therethrough which results in the accumulation of such fluid on the low pressure side of the pressure responsive diaphragm and thereby preventing normal operation thereof. It has also been found that such cracks, if permitted to occur in the diaphragm, will, through subsequent use of the diaphragm, propagate themselves to a degree causing the diaphragm to experience a degree of structural failure resulting in a total inoperativeness of the switch assembly.

It is believed that the said cracks are brought about because of the relatively high pressure exerted against a portion of the diaphragm which is unsupported during periods of operation. It should be remembered that during normal operation the diaphragm is cyclically exposed to both relatively high sustained hydraulic pressure as well as hydraulic pulsations and that these pulsations contribute to the total force which said unsupported portion is to withstand.

I has been previously noted that in order to reduce hysteresis, the pressure flexible diaphragms have been steadily reduced in cross-sectional thickness to where now it is not unusual to have such diaphragms of a thickness in the order of a few thousandths of an inch. The combination of repetitive cyclic operation of the pressure responsive diaphragm and the reduction in thickness of the material comprising the diaphragm has only served to enhance the frequency of occurrence of such disabling cracks as discussed above.

3,345,479 Patented Oct. 3, 1967 Accordingly, an object of this invention is to provide, in a fluid operated electric switch including a pressure responsive diaphragm, means for providing a support area for substantially all of the diaphragm material during periods of operation wherein relatively high hydraulic pressure is directed thereagainst.

Other objects and advantages of the invention will become apparent when reference is made to the following description considered in conjunction with the accompanying drawings wherein:

FIGURE 1 is an elevational view of an assembled fluid operated switch constructed in accordance with the teachings of this invention;

FIGURE 2 is a vertical cross-sectional view taken in the plane of line 2-2 of FIGURE 1, and looking generally in the direction of the arrows;

FIGURE 3 is a cross-sectional view, with portions thereof broken away, taken generally on the plane of line 3-3 of FIGURE 2 and looking in the direction of the arrows;

FIGURE 4 is a cross-sectional view taken in the plane of line 44 of FIGURE 2; and

FIGURE 5 is a fragmentary cross-sectional view, similar to FIGURE 2, illustrating another embodiment of the invention.

Referring now in greater detail to the drawings, FIG- URE 1 illustrates the fluid pressure operated switch 10 as being comprised of a cover member 12, formed of suitable electrical insulating material, through which a terminal member 14 extends. The insulating member 12 is suitably secured to a lower switch housing 16 which is preferably provided with an extending externally threaded portion 18 for mounting the switch to a suitable support structure which, in fact, may be a conduit leading to a source of hydraulic fluid.

As illustrated in FIGURE 2, the insulating member 12 is of a generally conical shape and is provided with a circular shoulder 20 at one end thereof. Insulator 12 is also provided with a centrally disposed bore 22 which accommodates a coiled compression spring 24. The terminal 14 has a stem 26 extending through the top of the insulating member 12 and the end of stem 26, which is within bore 22, is riveted or spun over in a well known manner against a metallic washer 28 in order to fasten terminal 14 to the insulating member 12.

The switch housing 16, which is preferably composed of metal, includes a hollow generally cylindrical portion 30 which may have externally formed recesses 32 adapted for engagement by a socket wrench for securing the switch assembly 10 as by a threaded portion 18 to a suitable sup porting structure. The cylindrical portion 30 is formed to provide a cavity 34 for receiving the shoulder 20 of the insulating member 12. A portion of the cylindrical section 30 may be peened or spun over as at as in order to retain housing 16 and insulator 12 in an assembled condition. The threaded extension 18 of switch housing 16 is provided with a centrally disposed bore 38 which, in operation, is in communication with a source of fluid so 5T0 direct such fluid under pressure to the pressure chamber 40 which is defined generally by the recessed surface 42 and diaphragm member 44.

The diaphragm member 44 is preferably comprised of a relatively thin circular sheet of high tensile strength plastic, such as polyethylene terephthalate which is commercially known as Mylar, retained generally peripherally between the insulating member 12 and switch housing 16. Further, an annular resilient member 46 is provided between the diaphragm 44 and switch housing 16 so as to provide some degree of resiliency thereby enabling diaphragm 44 to be peripherally secured without the danger q a) of cutting the diaphragm material as by pinching it between opposing surfaces 48 and 50 of members 12 and 16.

Insulator 12 also has a counterbore 52 formed in end surface 48 in a manner so as to be in substantial alignment with bore 22. The counterbore or recess 52 is of a size suflicient to closely receive therein a spring cup or retainer 54 which is secured to the diaphragm 44 as by a metallic rivet 56 and an intermediate member 58 which may be formed'of electrically insulating material. The intermediate member 58 may be made of the same material as is the annular resilient member 50 and may in fact, comprise a portion thereof, as illustrated in said United States Patent 2,898,418.

Recess 52 is formed to provide a shoulder 60' which determines the axial length of recess 52 and also serves as an abutment against which end surface 62 of spring cup 54 may abut.

The spring cup 54 is of a diameter which is slightly less than the diameter of the recess 52 and the axial length of the spring cup 54, as measured from, for example, the open end surface 62 to the opposite end surface 64, is preferably slightly less than the axial length of the recess 52 as determined by, for example, the surface of shoulder 60 and end surface 48 of insulating member 12.

Bore 38 has a contact member 66- suitably secured therein, as by a press fit, against relative axial movement. As illustrated in FIGURE 4, the contact member 66 is provided with a plurality of axially extending flutted portions 68 thereby enabling the flow of fluid under pressure from conduit or bore 38 through such flutted portions 68 and into pressure chamber 40.

Whenever insufiicient pressure exists within chamber 40, the force of spring 24 is such as to maintain the spring cup 54 in its lowermost position, which of course, is determined by contact 56 abutting against contact 66. At this time an associated electrical circuit (not shown) is completed through terminal 14, metallic washer 28, metallic spring 24, metallic spring cup 54, metallic rivet-contact 56, electrical contact 66, and the metallic housing 16. If threaded portion 18 is considered as an electrical ground, and if a vehicle dash panel mounted light bulb were electrically connected to terminal 14 and a source of electrical potential, then under the condition described above, and as illustrated in FIGURE 2, the said light bulb would become energized creating a visual indication that the hydraulic fluid pressure is insufficient or at least less than a predetermined minimum value.

Under the second operating condition, let it be assumed that a relatively high fluid pressure has been transmitted to chamber 46 and that the said high pressure is above the predetermined minimum value. At this time the high pressure in chamber 40 will act against diaphragm 44 thereby causing the diaphragm and spring cup 54 to move upwardly against the resistance of spring 24 thereby causing contact 56 to move away from contact 66. The upward movement of contact 56, of course, opens the circuit previously described and if the assumed light bulb were previously energized, it would now become deenergized.

Diaphragm 44, contact 56, spring cup 54, will continue to move upwardly against the force of spring 24 until such time as when end surface 62 abuts against shoulder 60 of recess 52. When this occurs, end surface 64 of spring cup 54 will be in substantial planar alignment with end surface 48 of insulating member 12 and thereby define practically a single continuous surface against which diaphragm 44 will be urged. As a consequence, substantially all of the material of diaphragm 44 will be supported by a surface on the low pressure side of the diaphragm thereby preventing the overworking of the diaphragm and eliminate the possibility of having disabling cracks occur therein. The only portion of diaphragm 44 that will be to any degree unsupported will be that area as may be defined by the clearance between the outer diameter of spring cup 54 and the diameter of recess 52. Accordingly, it

has been found that excellent results are obtained when the said clearance is of a magnitude less than the thick-' ness of the material forming said diaphragm 44. By establishing such a dimensional relationship between said clearance and material thickness of diaphragm 44 it then becomes impossible to have the diaphragm forced into said clearance by either the said high pressure fluid or hydraulic pulsations.

Various modifications of the invention are of course possible. However, the essence of the invention as herein disclosed resides in the provision of means, within the elements comprising the switch assembly, which will, during periods wherein said diaphragm 44 is exposed to relatively high pressures, tend to support as much of the diaphragm area as is possible. The provision of means for presenting a positive stop for an element which is movable with the diaphragm during periods of exposure to high pressure is of further benefit because the force which prevents further movement of the diaphragm can be for all practical purposes totally absorbed by the movable element and not the diaphragm member itself.

FIGURE 5, a fragmentary cross-sectional view similar to FIGURE 2, illustrates another embodiment of the invention. All elements which are like or similar to those of FIGURE 2 are identified with like reference numerals except as specifically noted to the contrary.

In the embodiment of FIGURE 5, the insulating member 12 has a cylindrical bore 70 formed therein which closely slidably receives a movable spring abutment and guide 72. The guide 72, formed to have an outer cylindrical guide surface 74 which is slidably received in bore 70, is illustrated as being of a generally cup-shape configuration so as to receive therein the end of spring 24. However, if desired, the guide may be of a disc-like shape and the end of spring 24 can be radially retained as by the upper portion 76 of the rivet-contact 56. As in FIG- URE 2, the rivet-contact 56 maintains the cup-guide 72 and diaphragm 44 in assembled relationship.

An additional member '78, which is preferably but not necessarily of metal, is also retained against the high pressure side of diaphragm 44 by rivet 56. As shown, member '78 is of an annular configuration, radiating outwardly of the center of rivet 56, having an outer diameter 80 which is substantially greater than the diameter of bore 70. Member 78, as will become evident, serves as an abutment member during certain periods of operation.

For example, as fluid under pressure is directed through conduit 38 into pressure chamber 40, diaphragm 44 is moved upwardly against the resistance of spring 24. The upward movement of diaphragm 44, guided by the slidable member 72, continues until the diaphragm 44 abuts against surface 48 and upper surface 82 of abutment or stop member 78 abuts against the lower surface of the diaphragm. At this time any additional force created by the fluid under pressure which would tend to move diaphragm 44 further upwardly is resisted not by exposing diaphragm 44 to forces which may exceed its elastic limit but rather by the abutting condition of stop member 80.

Although only two embodiments of the invention have been disclosed and described, it is apparent that other embodiments and modifications of the invention are possible within the scope of the appended claims.

I claim:

l. A fluid operated switch comprising a first housing second contact, a generally cylindrical spring perch secured to said diaphragm for engaging one end of said spring and being moveably disposed in said bore with the clearance between said bore and spring perch being less than the thickness of the material forming said diaphragm, and said spring perch and diaphragm being moveable to a position Where said spring perch substantially covers said bore and cooperates with said planar surface of the first housing member to provide a substantially continuous generally planar surface against which said diaphragm is urged when fluid is admitted to said fluid chamber.

2. A fluid operated switch according to claim 1 wherein said bore has an enlarged portion thereby providing a radially extending shoulder, said shoulder defining an abutment surface at an axial distance such that the spring 15 5 said diaphragm comprises a single sheet of material.

References Cited UNITED STATES PATENTS 2,898,418 8/1959 Byarn 200-83 FOREIGN PATENTS 1,120,862 3/1955 France.

BERNARD A. GILHEANY, Primary Examiner. G. MAIER, H. B. GILSON, Assistant Examiners. 

1. A FLUID OPERATED SWITCH COMPRISING A FIRST HOUSING MEMBER PROVIDED WITH A GENERALLY PLANAR SURFACE, A SECOND HOUSING MEMBER, A DIAPHRAGM HAVING ITS PERIPHERY COMPRESSED BETWEEN THE PLANAR SURFACE OF SAID FIRST HOUSING MEMBER AND SECOND HOUSING MEMBER, A FLUID CHAMBER FORMED BY SAID DIAPHRAGM AND SECOND HOUSING MEMBER, A FIRST CONTACT CARRIED BY SAID DIAPHRAGM CENTRALLY THEREOF, SAID SECOND HOUSING INCLUDING A SECOND CONTACT IN ENGAGEABLE RELATIONSHIP WITH SAID FIRST CONTACT A BORE FORMED IN THE FIRST HOUSING MEMBER AND EXTENDING THROUGH THE GENERALLY PLANAR SURFACE THEREOF, A SPRING SITUATED IN SAID BORE FOR CONTINUALLY URGING SAID DIAPHRAGM TOWARDS SAID SECOND CONTACT, A GENERALLY CYLINDRICAL SPRING PERCH SECURED TO SAID DIAPHRAGM FOR ENGAGING ONE END OF SAID SPRING AND BEING MOVEABLY DISPOSED IN SAID BORE WITH THE CLEARANCE BETWEEN SAID BORE AND SPRING PERCH BEING LESS THAN THE THICKNESS OF THE MATERIAL FORMING SAID DIAPHRAGM, AND SAID SPRING PERCH AND DIAPHRAGM BEING MOVEABLE TO A POSITION WHERE SAID SPRING PERC SUBSTANTIALLY COVERS SAID BORE AND COOPERATES WITH SAID PLANAR SURFACE OF THE FIRST HOUSING MEMBER TO PROVIDE A SUBSTANTIALLY CONTINUOUS GENERALLY PLANAR SURFACE AGAINST WHICH SAID DIAPHRAGM IS URGED WHEN FLUID IS ADMITTED TO SAID FLUID CHAMBER. 